Portable hand-drilling operations in the field, for example, at a construction site, have been known to suffer certain drawbacks stemming from difficulty in controlling the drill, particularly heavy drills, and difficulty in holding the workpieces. These problems not only can effect accuracy, quality and rate of production but they also seriously risk the safety of the drill operator.
During portable, hand-drilling operations, a reaction torque is generated in the drill and it is thus necessary for the drill operator to resist this torque with his body in order to hold the drill steady and to prevent rotation of the workpiece. This problem becomes most acute with heavy or large hand drills because the reaction torque can be great enough to strain the operator's hands, arms, shoulders or back. Moreover, if the drill cannot be steadied by the operator, the workpiece can rotate out of control causing a safety hazard while frustrating the drilling operation.
In order to combat the aforementioned problem, it is often necessary to drill holes at the same location in successively larger sizes (until the desired size is reached) in order to reduce the generated reaction torques. This, of course, seriously slows the rate of production and increases costs.
Other attempts to overcome the problem utilize magnetic devices for holding the drill in the proper position. However, such devices are heavy, cumbersome and costly and therefore not readily available at job sites.
To avoid the problem caused by a rotating workpiece, vises have been used. However, the problem of torque stress exerted on the operator's body still persists which can cause serious injury. Moreover, the use of vises seriously slows operations because for each drilling operation, the vise must be loosened, relocated and reset.